An electrical distribution system within an industrial, commercial or residential property starts at the utility service entrance and ends at the final utilization equipment or loads. The service entrance includes the utility company""s wattmeter or kWh meter. Beyond the utility company""s meter is a main circuit interrupting device, such as a circuit breaker. The main circuit breaker supplies power to a number of feeder circuits which in turn power a number of branch circuits. In a small system, such as a home, the main circuits directly feed individual branch circuits and no feeder circuits are employed. The electrical utilization loads are normally located on the branch circuits.
Typically, circuit breakers are used on the branch circuits to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high level short circuit condition. Circuit breakers employed in a commercial or residential setting are mounted in the panelboard. In residential or low ampacity circuit breakers, the circuit breakers are typically calibrated to a specific current value and with a specific trip time curve.
In contrast, industrial circuit breakers have used the concept of rating plugs with electronic trip units for many years to set the current ratings thereof. By inserting a rating plug, having a discrete resistance value, into a circuit breaker trip unit, the current rating is set for the industrial circuit breaker. Residential circuit breakers do not have the size or cost structure to accept rating plugs and consequently, residential circuit breakers are for practical purposes limited to a predetermined current rating.
Consequently, residential low ampacity circuit breakers have traditionally used the older thermal magnetic technology which does not have ready methods for changing the current rating of the circuit breaker. The thermal trip characteristic is operative in response to overload current of extended duration which heats a bimetal member, causing movement of the latter, which in turn releases a latch to trip open a set of contacts. The magnetic characteristic is operative in response to a sudden high magnitude current overload condition, and uses the magnetic field generated in a magnetic core to attract typically an armature, which movement releases the latch to open the contacts. As an example, the magnetic type actuation occurs in response to a short circuit wherein the hot line conductor becomes directly connected with ground or neutral, bypassing the load.
In either an industrial or residential environment, it is important to provide a management system which facilitates the monitoring and accurate control of electricity. The evolution and resulting dependency on digital computers and communication networks connecting these computers, such as data processing centers, has created a demand for high accuracy low ampacity circuit breakers to protect such critical load applications in branch circuits. Furthermore, advanced monitoring and remote control traditionally found in large, expensive industrial circuit breakers is desired for residential and commercial low ampacity circuit breakers without a premium price and size penalty.
It is known to employ electronic control, such as a computer, for controlling the solenoids of a plurality of circuit breakers in a panelboard. It is also known to employ the computer to monitor the status of the circuit breakers in a panelboard from the status contacts. What is needed is a low cost compact individual circuit breaker that allows for tailored protection to meet specific load requirements.
The above discussed and other drawbacks and deficiencies are overcome or alleviated by a panelboard configured for distributing electricity from a power source. The panelboard comprises: circuitry for distributing the electricity from the power source, the circuitry comprising a plurality of branch circuits for distributing electricity to associated loads; a plurality of branch circuit breakers, each branch circuit breaker intermediate the power source and the plurality of branch circuits; and an electronic control module for controlling the main circuit breaker and the plurality of branch circuit breakers, the electronic control module provides a protection function and a monitoring function of the circuitry, each branch circuit breaker of the plurality of branch circuit breakers includes; a pair of separable contacts, an electromagnetic actuator in electrical communication with the electronic control module for operably controlling the pair of separable contacts, and a current transformer configured to sense current on the circuitry to one of the associated loads.
A method is also described for providing overcurrent protection and control to an electric circuit with a single controller, the method comprising: receiving a trip setting value selected for each branch circuit of a plurality of branch circuits; storing the trip setting value in non-volatile memory; receiving a plurality of sensed signals from a current sensing device employed in the each branch circuit indicating a current therethrough; processing the plurality of sensed signals to detect an overcurrent condition in the each branch circuit; and generating a trip signal to an electromagnetic device coupled to separable contacts employed in each circuit breaker of the each branch circuit for interrupting current therein when an overcurrent condition is detected.